Complex data types can be specified as follows:
COMPLEX COMPLEX([KIND=]n) COMPLEX*s DOUBLE COMPLEX
If a kind parameter is specified, the complex constant has the kind
specified. If no kind parameter is specified, the kind of both
parts is default real, and the constant is of type default
complex.
DOUBLE COMPLEX is COMPLEX(8). No kind parameter is permitted for
data declared with type DOUBLE COMPLEX.